Probably need to GTFO [another how do I spin leaving question]
My answer to Probably need to GTFO [another how do I spin leaving question] on Ask MetaFilter
It strikes me that the core problem here is that your current company’s runway is privileged information: your current employer doesn’t need rumors about their financial health to start spreading. I think your instinct to avoid straight out saying that to other companies is very reasonable.
An honest alternative may to be say something like “I’m not convinced that my current company is on a successful path forward, and I’d rather work for a company like yours which I believe has a better chance at explosive success”. You’re not sharing privileged information, but you’re also not being misleading about your motivations. Plus you get to compliment your potential new employer at the same time.